A resident guest can paint fresh pixels after resize while capturePage's
native surface-copy request remains pending. The same failed guest returns
a fresh frame through frame subscription, so waiting for resize or another
animation frame does not correct the failing copy request.
Capture one subscribed frame within the existing five-second budget and
release the subscription on completion or cancellation. Preserve temporary
frame production and its original throttling policy. Remove viewport copy
retries and E2E screenshot polling; assert the resized image dimensions.
Refs #4866. Three full real-Electron browser journeys passed under Xvfb,
including physical clicks and fresh screenshots while the window is hidden.
Mohamed Boudra
d1a45f4dcb